1. Field of the Invention
The present invention relates to a method and a system for controlling a communication network and routers used in the network, and more particularly to a system and method for controlling call to mobile host through a mobile communication hierarchical network as well as another system and method for controlling a mobile communication hierarchical network.
2. Description of the Related Art
FIG. 1 is a block diagram illustrative of a conventional mobile communication network. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication.
As shown in FIG. 1, the mobile communication network includes a host network 1, plural routers Rn (n=1˜7), base stations BS1˜BS8, and a mobile host MH. The host network 1 may comprise a wide area network such as internet. The routers Rn provide multi-point connections between the host network 1 and the base stations BS1˜BS8. The routers Rn form a hierarchical network structure between the host network 1 and the base stations BS1˜BS8. The router R1 is highest level router. The routers R2 and R3 are middle level routers which are connected to the router R1 and dominated by the router R1. The routers R4, R5, R6 and R7 are lowest level routers, wherein the routers R4 and R5 are connected to the router R2 and dominated by the router R2, whilst the routers R6 and R7 are connected to the router R3 and dominated by the router R3. The base stations BS1 and BS2 are connected to the router R4 and dominated by the router R4. The base stations BS3 and BS4 are connected to the router R5 and dominated by the router R5. The base stations BS5 and BS6 are connected to the router R6 and dominated by the router R6. The base stations BS7 and BS8 are connected to the router R7 and dominated by the router R7.
The mobile host MH is connected through radio communication to any one of the base stations BS1˜BS8 to establish a link to the base station for communication through the host network 1 to other subscriber.
In accordance with this mobile communication network, the mobile host MH is managed in the current position thereof in activated state, or the mobile host MH is managed in paging area in inactivated state.
The routers R2 and R3 manage the respective paging areas. In FIG. 1, the mobile host MH is positioned in an area covered by the base stations BS1, BS2, BS3 and BS4, for which reason the mobile host MH is recorded in the paging area dominated by the router R2. If the mobile host MH moves from the first paging area dominated by the base stations BS1, BS2, BS3 and BS4 which are further dominated by the router R2 into a second paging area dominated by the base stations BS5, BS6, BS7 and BS8 which are further dominated by the router R3, then the router R3 registers the mobile host MH in the second paging area in accordance with a position recording message from the mobile host MH.
As shown in FIG. 1, it is assumed that the mobile host MH is recorded in the first paging area managed by the router R2. If a packet addressed to the mobile host MH for general calling is transmitted from a caller through the host network 1 to the router R1, then the router R1 selectively transfers the packet for the mobile host MH to the router R2 in the first step (1). The router R2 transfers the packet to all of the sub-ordinate routers R4 and R5 which are managed or dominated by the router R2 in the second step (2). The routers R4 and R5 further transfer the packet to all of the base stations BS1, BS2, BS3 and BS4 which are managed by the routers R4 and R5 in the third step (3).
The base stations BS1, BS2, BS3 and BS4 perform general calling to the mobile host MH, whereby any connectable one of the base stations BS1, BS2, BS3 and BS4 establishes a link to the mobile host MH in the fourth step (4). In FIG. 1, the base station BS3 established the link to the mobile host MH. The mobile host MH transmits a position recording message to the base station BS3 in the fifth step (5). The base station BS3 transfers the position recording message to the router R5 in the sixth step (6). The router R5 further transfers the position recording message to the router R2 as well as updates routing information to the mobile host MH in the seventh step (7). The router R2 updates routing information to the mobile host MH. As a result, the communication route of the router R1, the router R2, the router R5 and the base station BS3 is established. The routing information is an information which indicates a route up to a packet-destination. The routing information is recorded on a routing table of the router.
FIG. 2 is a sequence diagram illustrative of sequential operations of the above described conventional mobile communication hierarchical network shown in FIG. 1. As shown in FIG. 2, if the packets are discontinuously transmitted from the host network 1, then the routers R1, R2, R4 and R5 transfer the received packets to the subordinate routers or the managing base stations BS every time when the packets are transmitted from the host network 1 until any link is established between the base station and the mobile host MH.
As described above, in accordance with the conventional mobile communication hierarchical network, if the packet addressed to the mobile host MH in the stand-by state is transmitted from the caller through the host mobile MH, then the router managing the paging area, on which the stand-by state mobile host MH is recorded, performs the general calling the sub-ordinate network managed by this router for calling the host mobile MH, wherein the packet addressed to the mobile host MH is transferred to all of the base stations managed by this router.
It is, however, general that the caller transmits the packets through the host network 1 without consideration of loads to the hierarchical network, whereby the packet for general calling to the mobile host MH causes the increase in the load to the hierarchical network.
FIG. 3 is a block diagram illustrative of another conventional mobile communication network. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication.
As shown in FIG. 3, the mobile communication network includes a host network 1, plural routers Rn (n=1˜7), base stations BS1˜BS8, and a mobile host MH. The host network 1 may comprise a wide area network such as internet. The routers Rn provide multi-point connections between the host network 1 and the base stations BS1˜BS8. The routers Rn form a hierarchical network structure between the host network 1 and the base stations BS1˜BS8. The router R1 is highest level router. The routers R2 and R3 are middle level routers which are connected to the router R1 and dominated by the router R1. The routers R4, R5, R6 and R7 are lowest level routers, wherein the routers R4 and R5 are connected to the router R2 and dominated by the router R2, whilst the routers R6 and R7 are connected to the router R3 and dominated by the router R3. The base stations BS1 and BS2 are connected to the router R4 and dominated by the router R4. The base stations BS3 and BS4 are connected to the router R5 and dominated by the router R5. The base stations BS5 and BS6 are connected to the router R6 and dominated by the router R6. The base stations BS7 and BS8 are connected to the router R7 and dominated by the router R7.
The mobile host MH is connected through radio communication to any one of the base stations BS1˜BS8 to establish a link to the base station for communication through the host network 1 to other subscriber.
The mobile host MH transmits a position recording message to the base station BS2 in the first step (1). The routers Rn update the respective routing informations based on the position recording message from the mobile host MH and also transfer the position recording message to the upper level routers in the second, third and fourth steps (2), (3) and (4). The routing information is an information which indicates a route up to a packet-destination. The routing information is recorded on a routing table of the router.
When the position recording message reaches the top level router R1, a communication route between the host network 1 and the mobile host MH is established. In FIG. 3, the communication route as established includes the mobile host MH, the base station BS2, the router R4, the router R2 and the router R1. FIG. 4 is a block diagram illustrative of communication processes of the conventional mobile communication network of FIG. 3. As shown in FIG. 4, the packet addressed to the mobile host MH is transferred from the host network 1 through the router R1, the router R2, the router R4 and the base station BS2 to the mobile host MH sequentially.
If, accidentally, at least one router on the established communication route between the host network 1 and the mobile host MH becomes failure, then the communication route becomes disconnect. This conventional communication network has no further available route between the base station BS2 and the host network 1. For this reason, it is necessary to reset the failure router and re-establish the communication network between the host network 1 and the mobile host MH before the communication route between the mobile host MH and the host network 1 is established by re-updating process by the routers Rn for re-updating the routing information based on the position record message from the mobile host MH. If at least any one of the router on the established communication route becomes once trouble and the communication route becomes lost, then no communication can be made between the mobile host MH and the host network 1 until the communication route between the mobile host MH and the host network 1 is re-established by re-updating process by the routers Rn for re-updating the routing information based on the position record message from the mobile host MH.
In FIGS. 3 and 4, only the single mobile host MH is shown, even actually a plurality of the mobile host MH are generally the subject to the communication through the above network. The plural mobile hosts MH transmit respective plural position recording messages which are transferred through the hierarchy-networked routers Rn to the host network 1 for re-establishment of the communication route. The upper level router is likely to receive many position recording messages from the plural mobile hosts MH. This means that the transmissions of the many position recording messages from the many mobile hosts MH increases the load to the upper level router.
As described above, if at least any one of the router on the established communication route becomes once trouble and the communication route becomes lost, then no communication can be made between the mobile host MH and the host network 1 until the communication route between the mobile host MH and the host network 1 is re-established by re-updating process by the routers Rn for re-updating the routing information based on the position record message from the mobile host MH.
Further, the plural mobile hosts MH transmit respective plural position recording messages which are transferred through the hierarchy-networked routers Rn to the host network 1 for re-establishment of the communication route. The upper level router is likely to receive many position recording messages from the plural mobile hosts MH. This means that the transmissions of the many position recording messages from the many mobile hosts MH increases the load to the upper level router.
FIG. 5 is a block diagram illustrative of still another conventional mobile communication network. This mobile communication network is generally used for a management system for managing positions of mobile telephones or automatic cars. This mobile communication network utilizes transmission control protocol/internet protocol (TCP/IP) for realizing a packet communication.
As shown in FIG. 5, the mobile communication network includes a host network 1, plural routers Rn (n=1˜7), base stations BS1˜BS8, and a mobile host MH. The host network 1 may comprise a wide area network such as internet. The routers Rn provide multi-point connections between the host network 1 and the base stations BS1˜BS8. The routers Rn form a hierarchical network structure between the host network 1 and the base stations BS1˜BS8. The router R1 is highest level router. The routers R2 and R3 are middle level routers which are connected to the router R1 and dominated by the router R1. The routers R4, R5, R6 and R7 are lowest level routers, wherein the routers R4 and R5 are connected to the router R2 and dominated by the router R2, whilst the routers R6 and R7 are connected to the router R3 and dominated by the router R3. The base stations BS1 and BS2 are connected to the router R4 and dominated by the router R4. The base stations BS3 and BS4 are connected to the router R5 and dominated by the router R5. The base stations BS5 and BS6 are connected to the router R6 and dominated by the router R6. The base stations BS7 and BS8 are connected to the router R7 and dominated by the router R7.
The mobile host MH is connected through radio communication to any one of the base stations BS1˜BS8 to establish a link to the base station for communication through the host network 1 to other subscriber.
The mobile host MH transmits a position recording message to the base station BS linked to this mobile host MH in a first step (1). The position recording message is transferred from the linked base station through the routers from the lowest level to the highest level, thereby establishing the communication route between the host network 1 and the linked base station BS. The routing information is an information which indicates a route up to a packet-destination. The routing information is recorded on a routing table of the router.
For example, as shown in FIG. 5, a communication route has been established which includes the router R1, the router R2, the router R4, and the base station BS2 linked to the mobile host MH. The packet addressed to the mobile host 1 is transmitted from the host network 1 to the router R1. The router R1 transfers the received packet to the router R2 based on the routing information held itself in the first step (1′). The router R2 transfers the received packet to the router R4 based on the routing information held itself in the second step (2′). The router R4 transfers the received packet to the base station BS2 based on the routing information held itself in the third step (3′). The base station BS2 transmits the received packet to the mobile host MH. Namely, the packet is transferred from the host network 1 through the router R1, the router R2, the router R4 and the base station BS2 to the mobile host MH.
FIG. 6 is a block diagram illustrative of operation of the conventional mobile communication network of FIG. 5. The mobile host MH moves from a radio area covered by the base station BS2 to another radio area covered by the base station BS3. Adjacent two radio areas covered by the adjacent two base stations are generally bounded by an overlap boundary area, even this overlap boundary area is not illustrated in FIG. 6. The mobile host MH establishes a link to the base station providing a highest radio intensity that is sensed by the mobile host MH.
When the mobile host MH moves from the area covered by the base station BS2 to the other area covered by the base station BS3, then the mobile host MH has lost the link to the base station BS2 and establishes a link to the base station BS3. The mobile host MH further transmits a new position recording message to the base station BS3. The base station BS3 transfers the received new position recording message to the router R5. The router R5 further transfers the received new position recording message to the router R2. The router R2 further transfers the received new position recording message to the router R1. As a result, a new communication route is established which includes the host network 1, the router R1, the router R2, the router R5 and the base station BS3 to the mobile host MH.
If the mobile host MH moves from the radio area covered by the base station BS2 to the other radio area covered by the base station BS3 during the transfer of the packet through the hierarchical-structure of the routers Rn, then the packet is transferred through the old communication route including the router R4 and the base station BS2, because a newly communication route including the router R5 and the base station BS3 could not be established. Since the mobile host MH has lost the old link to the base station BS2 and has already established a new link to the base station BS3, then the mobile host MH could not receive the packet from by the base station BS2.
Accordingly, in accordance with the conventional mobile communication network, if the base station having the current link to the mobile host MH is changed to the other base station establishing a new link to the mobile host MH, during the transfer of the packet through the mobile communication network, then the mobile host MH could not receive the packet. Namely, a problem with the packet loss is raised. It is desirable to reduce the probability of rising the problem with the packet loss.
In the above circumstances, the development of novel method and system for controlling the mobile communication hierarchical network free from the above problems is desirable.